In the above cited patent applications as well as the article, circuits are described for separating force signals from angular rotation signals from the output of a single or a pair of accelerometers that are either being cyclically rotated or vibrated at a constant frequency .omega.. In these circuits the analog output signal from the accelerometer(s) is integrated over the period T of one cycle of .omega. by an integrating circuit and then applied to a sample and hold circuit to obtain a specific force signal F. At the same time, the output signals from the accelerometer(s) are multiplied by the zero mean function signal sgncos.omega.t. This signal is then integrated over the period T and applied to a sample and hold circuit. The resulting signal, as described in detail in the above cited patent applications and article, represents the rotation of the accelerometer(s) with respect to the force sensing axis of the accelerometer(s).
Due to the fact that inertial navigation systems, for which the above described force and angular rate measuring systems find particular application, require digital inputs at some point because they employ digital computers, it is quite often necessary to convert the voltage or current output signals from the accelerometers representing specific force and angular rate into digital form.